STM32F411 Bootloader hangs

[Gifford]

Hi there!

I've created a custom STM32F411CEU6 Board with external HSE und LSE. While the HSE works when running my user program, the Bootloader hangs within boot phase (i think).

When starting bootloader, BOOT0=1 und BOOT1=0. I powered direcly on VDD, no USB. I received no answer on both uarts after sending 0x7F. I also can't connect via stmcubeprogrammer. Only can only connect with stlinkv2.

I think it may be a hardware issue, but I can't find a solution.

Crystal 25Mhz: https://atta.szlcsc.com/upload/public/pdf/source/20240329/19D5F850207469550BEB00D7DFEDBC7A.pdf

LSE:

https://atta.szlcsc.com/upload/public/pdf/source/20240418/0E0FF5F0356BA3753F616001439D1416.pdf

[Gifford]

No, i havn't such a crystal in that footprint. I choosed the 25Mhz crystal because of the black pill board. It uses the same frequency and all works fine. AN2606 mentions that the external clock can be up to 26 Mhz.

Do you think my choosed crystal could be a "unsuitable" brand?

[AScha.3]

No, i just asked because 25M is close to upper limit (26) and standard crystals are usually made only up to 30M in fundamental oscillation . So the range 8M to 16M is what i choose, to stay away from all possible limits/problems.

Sometimes even 24M crystals are 8M , running on 3. overtone for 24M ; if you have such a crystal, its possible , its oszillating on fundamental, not on the desired 3rd harmonic. Thats why i wrote: try a (lower) standard frequency, just to prove, thats not the problem.

(I had one time such a case: ordered 24M crystal, fundamental mode; but got it and it was 8M, 3rd overtone, for 24M.)

So did you check , maybe on MCO, the crystal is really at 25M ?

[Gifford]

yes, I checked. While running user program it runs at 25M. But it's not oscillating on usb bootoader....

maybe an issue with the startup time from crystal??

[AScha.3]

Maybe.

So try "standard" 8MHz , or 16M crystal.